The principal limitation in the design of microwave (radio frequency) anechoic chambers is the amount of suppression of sidewall reflection achievable with various absorbers and chamber geometry. The geometric design of an anechoic chamber is directly controlled by economic considerations. Generally speaking, the larger the chamber room, the greater is the thickness of the absorber material that can be used, and thus the higher is the performance of the chamber. However, the absorber material is very expensive, thus limiting the practical dimensions of the chamber. In addition, a cubicle chamber is more effective than a smaller chamber of the same length but having a narrower width. The ratio of the length to the width is referred to as the "aspect ratio." The higher the aspect ratio, the greater the angle of incidence of radiation on the sidewalls deviates from normal. At very shallow angles of incidence, the absorbing capability of the absorber material falls off dramatically.
There is a need therefore for a chamber geometry, and an absorber element which can be incorporated in such chamber geometry, which in effect re-orients the surface experienced by the radiation wave front as it impinges on the sidewalls of the chamber, effectively shifting the angle of incidence at such sidewall areas from a shallow angle to an angle more closely approaching orthonormal.